The invention relates to an arrangement for mixing multi-component compositions, in particular dental impression compositions, which comprises a component-extruding device and a mixer. The inlet openings of a mixer can be connected to the outlet openings of the extruding device assigned to the components. For example, the inlet openings of the said mixer may be designed in the form of pipe spigots which are cylindrical or slightly conical on the outside and can be inserted in a sealing manner into the outlet openings of the extruding device. The outer surfaces of the pipe spigots and the inner surfaces of the outlet openings interact as guiding surfaces for the connection. The guiding surfaces of one part are designed to complement the guiding surfaces of the other part.
The extruding pressure, which has a tendency to lift the mixer off the extruding device, acts in the region of the openings. Therefore, a device which presses the mixer against the extruding device counter to this force must be provided. In order that the sealed connection is ensured, this pressing device must permanently ensure adequate force and accuracy (EP-B-492 412). It is known (DE 3237353 A1) to arrange the openings in such a way that they penetrate the guiding surfaces transversely. The openings are offset axially with respect to one another in order to prevent the two components from coming into contact in the inlet region and hardening there. In this arrangement, the compressive forces acting in the openings only partially cancel one another out.
According to the invention, the openings open out in a diametrical arrangement in mutually opposite surface portions of the guiding surfaces. The compressive forces acting in the openings thereby largely cancel one another out. The holding devices, which are provided for securing the connecting position of the openings, are subjected only to the load of that force which corresponds to the pressure drop in the mixer. Also provided within the inlet region of the mixer is a wall, the extent of which is large enough that the limit of the region in which the hardening of the composition is to be expected is sufficiently far away from the outlet openings and inlet openings.
If a dynamic mixer is concerned, this wall is expediently arranged at that end plate of the mixer which forms the bearing opening for the mixer shaft. If a static mixer is concerned, an insert which is inserted into the relevant end of the mixer housing and on which this wall is arranged may be provided.
The arrangement is expediently symmetrical with respect to the centre axis of the mixer. The openings open out laterally, transversely with respect to this axis.
In the case of a particularly advantageous embodiment of the invention, the guiding surfaces arranged on the one hand on the extruding device and on the other hand on the mixer define a pushing-in direction running transversely with respect to the center axis of the mixer and transversely with respect to the opening orifices. Transversely with respect to this pushing-in direction (i.e. in the direction of the mixer center axis), they are positively connected to one another.
In the case of another embodiment of the invention, the guiding surfaces are essentially cylindrical and can be locked in the connected position by a bayonet fixing or the like.